New upstream version 1.9

[debian/gzip] / lib / xalloc-oversized.h

diff --git a/lib/xalloc-oversized.h b/lib/xalloc-oversized.h
index d81a8471d377d573ebd723bd1de15f934957fcee..3426e10f4d2816e53f9af67d9de78c4a329850c2 100644 (file)
--- a/lib/xalloc-oversized.h
+++ b/lib/xalloc-oversized.h
@@ -1,6 +1,6 @@
 /* xalloc-oversized.h -- memory allocation size checking
 
-   Copyright (C) 1990-2000, 2003-2004, 2006-2016 Free Software Foundation, Inc.
+   Copyright (C) 1990-2000, 2003-2004, 2006-2018 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -13,35 +13,48 @@
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
 
 #ifndef XALLOC_OVERSIZED_H_
 #define XALLOC_OVERSIZED_H_
 
 #include <stddef.h>
+#include <stdint.h>
 
-#ifndef __has_builtin
-# define __has_builtin(x) 0
+/* True if N * S would overflow in a size_t calculation,
+   or would generate a value larger than PTRDIFF_MAX.
+   This expands to a constant expression if N and S are both constants.
+   By gnulib convention, SIZE_MAX represents overflow in size
+   calculations, so the conservative size_t-based dividend to use here
+   is SIZE_MAX - 1.  */
+#define __xalloc_oversized(n, s) \
+  ((size_t) (PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX - 1) / (s) < (n))
+
+#if PTRDIFF_MAX < SIZE_MAX
+typedef ptrdiff_t __xalloc_count_type;
+#else
+typedef size_t __xalloc_count_type;
 #endif
 
-/* Return 1 if an array of N objects, each of size S, cannot exist due
-   to size arithmetic overflow.  S must be positive and N must be
-   nonnegative.  This is a macro, not a function, so that it
-   works correctly even when SIZE_MAX < N.
+/* Return 1 if an array of N objects, each of size S, cannot exist
+   reliably due to size or ptrdiff_t arithmetic overflow.  S must be
+   positive and N must be nonnegative.  This is a macro, not a
+   function, so that it works correctly even when SIZE_MAX < N.  */
 
-   By gnulib convention, SIZE_MAX represents overflow in size
-   calculations, so the conservative dividend to use here is
-   SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value.
-   However, malloc (SIZE_MAX) fails on all known hosts where
-   sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for
-   exactly-SIZE_MAX allocations on such hosts; this avoids a test and
-   branch when S is known to be 1.  */
-#if 5 <= __GNUC__ || __has_builtin (__builtin_mul_overflow)
+#if 7 <= __GNUC__
 # define xalloc_oversized(n, s) \
-    ({ size_t __xalloc_size; __builtin_mul_overflow (n, s, &__xalloc_size); })
-#else
+   __builtin_mul_overflow_p (n, s, (__xalloc_count_type) 1)
+#elif 5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__
 # define xalloc_oversized(n, s) \
-    ((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))
+   (__builtin_constant_p (n) && __builtin_constant_p (s) \
+    ? __xalloc_oversized (n, s) \
+    : ({ __xalloc_count_type __xalloc_count; \
+         __builtin_mul_overflow (n, s, &__xalloc_count); }))
+
+/* Other compilers use integer division; this may be slower but is
+   more portable.  */
+#else
+# define xalloc_oversized(n, s) __xalloc_oversized (n, s)
 #endif
 
 #endif /* !XALLOC_OVERSIZED_H_ */